Technical Field
The present disclosure relates to the fabrication of low power tunneling diodes and tunneling field effect transistors (TFETs) used in conjunction with graphene sensors for biological applications.
Description of the Related Art
Tunneling diodes and TFETs are microelectronic devices that switch on and off in response to a relatively low applied voltage, making them good candidates for low power applications. While a state-of-the-art 3-D multi-gate transistor requires applying about 0.8 V to switch on, a tunneling device requires applying less than about 0.5 V. Consistent with the reduction in applied voltage, the TFET device achieves the same performance as a bulk silicon MOSFET device using about half the energy, when operated in a low-energy regime. As a result, less power is consumed by the tunneling device and less power is dissipated as heat. Thus, the TFET is advantageous for use within a certain energy range, e.g., for relatively low energy applications. [A. M. Ionescu and H. Riel, “Tunnel Field-Effect Transistors as Energy-Efficient Electronic Switches,” Nature: 479, pp. 329-337, Nov. 17, 2011, herein incorporated by reference in its entirety].
Graphene has drawn attention in recent years for use in FETs due to its extraordinary material properties, as shown in FIGS. 1A and 1B. Graphene is a monolayer of carbon graphite atoms arranged in a honeycomb crystal lattice (FIG. 1A). Crystalline graphite is made of stacked sheets of graphene. Although graphene was known for many years, a single graphene sheet was not isolated until 2004, for which a Nobel Prize in physics was awarded in 2010. Mechanically, graphene is one of the strongest materials ever tested, more than 100 times stronger than steel (if steel could be made as thin as a graphene sheet). Graphene sheets are flexible and can be rolled into carbon nanotubes or formed into nanowires or graphene nanoribbons. Graphene is also very lightweight, weighing only 0.77 mg per square meter (FIG. 1B).
Graphene also has favorable electronic properties. For example, graphene has high electron mobility over a wide temperature range, lower resistance at room temperature than any known material, and low noise. Furthermore, a graphene film can be epitaxially grown on silicon carbide (SiC) by heating the SiC in a vacuum chamber to temperatures exceeding 1100° C. The graphene film can then be patterned using conventional microelectronics techniques. Graphene has been studied as a material for use in microelectronics, such as in graphene field effect transistors (GFETs) [Meric, et al., Proceedings of the IEEE IEDM Conference, Dec. 5-7, 2011, pp. 2.1.1-2.1.4].